Let’s talk about Godwits

19 08 2014

 “In practical life we are compelled to follow what is most probable ; in speculative thought we are compelled to follow truth.”

– Baruch Spinoza

WARNING! The following post is highly speculative. If you consider yourself a pure scientist, do not read it.

After several days with constant showers and strong westerlies (= no ringing), I’ve got plenty of time to read random papers. It’s actually a completely different activity than reading papers “at work”; if you are not interested in what you are reading, you just leave it and go for another one. What usually happens is that you start reading about migration and end up with evolutionary ecology. Coincidence? I don’t think so.

This week, however, it was the oposite for me. I came across a couple of papers about niche filling, diversification and stability (Stigall 2014 and Price et al 2014) and they were the starting signal of what led me to read about Bar-tailed godwit migration. Since the same weather that forces me to read also forces the godwits to stop in the Peninsula, when the rain gave a break I went to Nabben to enjoy big numbers of them in beautiful summer plumage. Sometimes theory plus field observations equals conclusions and, since here in my blog I’m allowed to be especulative, let’s theorize about Nabben’s Bar-tailed godwits.


The first flock I saw was peacefully feeding in the [for once in a lifetime] quiet golf course and what stroke me in the beginning was the overall size difference between the brighter summer-plumaged and the grey winter-plumaged individuals, the latter being bigger. Differences were especially noticeable in bill lenght and depth. As usual in waders, females have a longer and deeper bill and are duller in plumage, so in the photo below there is 1 female and 4 males.  The whole flock was made out of 12 males and 2 females. What’s the reason for such a biased sex-ratio? According to BWP (Cramp et al. 1983), there is not a big difference in parental care in Bar-tailed godwit, so both male and female stay with the youngsters until they fledge. Hence, there shouldn’t be a sex-related difference in departure dates. The reason might have something to do with their feeding ecology and subsequent sexual segregation. Several studies (e.g. Both et al. 2003, Catry et al. 2012) have pointed out a difference in foraging habitat due to larger food requirements in females (because of their bigger size) and they are the ones choosing the place. Seemingly, females usually forage along the rich waterline, whereas males have to get along with exposed mudflats and grassy meadows. A golf course is probably not the best place to find food so it’s not that surprising that that flock was mainly made out of males.

female plus for males

Let’s focus on males for a while. Their bill is more curved than that on females, and impression accentuated by its shorter lenght. Ferns & Siman 1994 studied feeding techniques and resources and related them to bill shape and found that curved bills were useful to get food from cavities and confined spaces. Makes sense! Males are feeding in poorer habitats and have a stronger need to actually look for food instead of just find it as females do in richer areas with their straighter bill. Moreover, there was a difference in bill shape even within males. I’ve tried to sort the different kinds of bill I saw in males in the crappily made collage below. In the top, bills that looked almost straight; in the middle, bills that looked straight but curved in the end; in the bottom, bills that looked wholly curved. I know, differences are subtle, but, quoting whatever famous documentarist “in nature, a milimiter makes the difference between life and death”. Don’t google it, I just made it up, but it sounds likely, doesn’t it?


Anyway, guess what, I don’t know about the bird in the top left, but the bird in the top right showed the wornest primaries among the flock, especially the outer ones in what gave the impression of a moult limit. Moreover, and always among the males, it was the one with a duller plumage despite it didn’t show any winter body feather. So it’s my strong opinion that this bird is a 1st summmer: worner primaries (maybe fresh inner due to an earlier, before migration, moult) and duller plumage than adults. Check the difference in wear level in outer primaries in the photo below, also head and body plumage. The conclusion I temptatively get from this is that the bill gets more curved with age. It also makes sort of sense: females will be always dominant, pushing males towards a place where they need a curved bill. Lammarck would say young birds change the shape of the bill to make it fit with the habitat they are foraging in. Maybe… but a modern approach would probably say that only juveniles with curved bills reach the adult age. Good luck to our misfit friend!


Let’s now focused on putative adult males and their shinny bellies. Piersma & Jukema 1993 suggested that the brightness of the orange in summer-plumaged  Bar-tailed godwit was an honest signal in relation to migratory skills. Birds start with their pre-breeding (pre-alternate for the yanks) moult in winter quarters, they suspend it before departing and then congregate in places such as the Wadden Sea (north central Europe) to finish it. Despite moult only takes an extra 7% of energy, only the individuals in good physical condition (this is, more skillful in terms of feeding or flying performances) can afford it. The bird in the right of the photo below is obviously brighter than the other two, despite all three of them presumably belong to the same age and sex classes. I wonder if it has something to do with the mentioned study…

breast color

And now we are talking about migration, it’s worth saying that Bar-tailed godwit still holds the longest non-stop flight record: 11.500 km. from Alaska to New Zealand! Hedenström 2010 tries to answer at least some of the thousands of questions that emerge from this record, but ends up saying that not even the extremely especialized physiology of Bar-tailed godwits can explain such a success. Maybe some help from the weather? Let’s leave this questions for the next wave of rain…

Gull-watching in Sweden

12 08 2014

“They all should be called Larus larus – Guillermo Rodríguez Lázaro

Looking for gulls doesn’t sound like a good way to spend a day off after several days of hard ringing in Flommen reedbed but, since it had been a long time since my last serious gull-watching session, I really enjoyed yesterday’s trip to Shimrishamn and the east coast of Skåne. First of all, I should say thank you very much to Walter Wehtje for such a nice day off the peninsula.

We arrived to Simrishamn harbor quite late in the morning, but there were still some gulls to look at. There we found our first 2 juveniles Caspian gull, but one of them quickly hid away behind the breakwater and the other was boringly sitting among Great black-backeds and Herrings. Nice re-encountering with this fresh juvenile plumage, one of the rarest in Spain, where it seems restricted to early arrivals to the NW coast. Despite the black mask lacking in most of 1stW, it keeps its depressive appearence that makes me like them and feel sorry for them at the same time.

cachinnans juvenile1

After half an hour uselessly waiting for the bird to stand up and do something, we head south following Ulrik‘s suggestion, stopping to check each flock of gulls sitting on the shore. The next time we had success was around Brantevik harbor, where we found another juvenile Caspian plus a 1st summer bird. I didn’t know in which stage of moult would I find these 2cy now, but I had expected them to be done with their complete. However, this 1stS was still growing p9 and the number of unmoulted secondaries was surprisingly (or maybe not that much…) high. The tail was also being renewed.

cachinnans 1stS

While waiting for this bird to fly, I took a look at the Canada geese that were peacefully swimming around the rocks. Walter had already seen one putativa hybrid Greylag x Canada, but there was actually a whole clutch of them. The freaky family was made out of a presumed male Canada, a really confused presumed female Greylag and 5 odd-looking fledglings. Dear geese: please, stop doing that.

hybrid geese

Our next stop was at Skillinge. There was nothing in the harbor, but lots of gulls south of it and it turnt out to be the best place among the ones we checked. We spotted a couple more juvenile Caspian, one of them giving close views of its whiter head and genuine bill profile.

cachinnans juvenile2

It was then when Oscar Danielson suddenly appeared with a bag of trashy food, ready to re-join Ulrik after a brief but profitable incursion into civilization. They had been birding even further south and seen almost the same number if Caspian gulls we had seen. We saw together the stincky Ruddy shelduck that Emil and Erik had found something like a week ago and we came back to gull-watching since the most interesting stuff (this is, the less identifiable stuff) was still to come. After a couple more juvenile Caspian (between Oscar and Ulrik and us, we might ended up seing like 20 of them), I spotted an adult bright ‘yellow-legged’ gull sitting on a rock. It went for a short flight and landed nearby. Here in an out-of-focus photo just to compare leg colour.


And here chasing an adult Herring showing its wing tip pattern. As can be seen, the mirror in p9 is quite big and it lacks the subterminal black band in p10. This pattern has been described for eastern Yellow-legged gulls (by Chris Gibbins, for instance: here).


However, in this last record shot, it’s posible to see the recently grown p5 with just an unsolid black subterminal band. This, together with the same mantle coloration as the Herrings around, makes me sceptic of it being a Yellow-legged gull, or at least a pure one. All in all, keeping in mind we are in Sweden and it was indeed in the Baltic were we saw this bird, I’d call it omissus or yellow-legged type Herring.


When we thought this was gonna be the most interesting bird of the day, Ulrik spotted a 2cy whatever that looked tricky. The overall dark coloration and the Caspish jizz made me think about Heuglin’s, but the bird was too advanced in primary moult and too delayed in body moult. Ulrik managed to take some flight photos where you can see a really dark underwing and completely dark new primaries. p9 and p10 are still juvenile, all GCs seem to be moulted and the white bar in MCs might be a whole line of feathers missing, so moult pattern fits with both Herring and intermedius Lesser black-backed. The coloration of the new feathers points to LBB but structure and especially bill shape (with such a pronounced gonys) points to nominate Herring. My conclusion: I don’t know.



So we left having seen plenty of interesting stuff, including these 2 youngsters. Don’t ask me what the hell are they doing in the photo. Don’t ask me about Oscar’s t-shirt or Ulrik’s cap neither. Those are even bigger misteries than some of the trickiest gull’s identity…

ulrik and oscar

Quality time

3 08 2014

 “We were right we were giving, and this is how we kept what we gave away.”

– Comes a time, Neil Young

It’s been already a month since all these events happened, but I’ve kept them in my mind since they are gonna be one of the best memories I’d preserve from 2014. After a busy spring  coming and going from Barcelona to elsewhere, it happened that Stephen suddenly came to visit us and I had not got the time to plan the trip properly. Neither had Marc and Martí, and hence we ended up in Vall d’Aran looking for some nice birds/butterflies/orchids but basically spending some quality time together. It was the first time that Marc, Martí, Stephen and me were at the same time in the same spot but I’m pretty sure it’s not gonna be the last one.

The first thing we did was to ring a Rock bunting. Stephen had fallen in love with the species in the very first time he came to Catalonia. Now he is not in a hurry to see everything, we can spend some time to actually look at the birds. As expected, when we caught it and realized it was a boring adult (3+, Euring 6, 2nd cycle, …) Stephen recognized it was not that nice and claimed for a 2nd year. After we had politely suggested him to go and screw himself, we left the area and finally faced the Pyrenees.

The first stop was at a very nice place Marc knew was plenty of Pyrenean brook salamander Calotriton asper. Nice to see them but once you’ve seen one, you’ve seen them all. In case you wonder, it’s Stephen holding the newt in front of his brand new t-shirt he had bought in London airport.

calotriton asper

In Vall d’Aran we saw some Lammergeiers, a Cinereous vulture, Citril finches and quite a lot of orchids. Since Martí is been very into orchids lately, it was nice to learn from him. As I can’t be arsed to make the usual collage that usually ilustrates this kind of paragraphs, I will just post a photo of the one I liked the most: Sword-leaved Helleborine Cephalanthera longifolia.

cephalanthera longifolia

But the best was this Black hairstreak Satyrium pruni: the first record for Catalonia! More on that soon…


After some Black-bellied sandgrouses, whiterby Reed buntings and displaying Red-necked nightjars in Lleida steppes, we came back to Barcelona to target Pekin robin (currently Red-billed leiothrix or something like that). We failed despite there were several singing around. However, we caught a couple of Sardinian warblers and some baby Firecrest that made Stephen happy. So did the omelette and the Iberian ham we got for dinner.

We still had a day to fill up some lagoons: we still needed to see a male Roch thrush. We went to a place near Marc’s area where they used to breed. Nowadays they don’t, but it’s still an interesting Mediterranean bushland area good for Ortolan bunting, Western orphan warbler, Red-rumped swallow, blue rock thrush… We put up the nets and managed to catch a 2cy male Western Orphean, an Iberian subalpine wabler (currently inornata iberiae) and a Red-legged partridge. To finally see a male Rock thrush we had to go up to Turó de l’Home, the highest peak in Montseny mountains. Fortunately, we found one almost immediately and it ended up being the last bird of the trip.

sylvia hortensis

Almost one month later, and just before coming to Sweden, I came back to Vall d’Aran, this time with Laura. The air, the wildlife and the landscapes of this area is perfect for a reset in life. We didn’t look for anything in particular, our only purpose was to be there and forget about the stressful city, without cell phone signal, using electricity only for listening to music. We managed, and now I feel ready for the start of a new ringing season in Falsterbo.

Lycaena virgaureae

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